Method for electrolytic production of iron from iron sulfate solutions



Patented Jan. 26, 1954 METHOD FOR ELECTROLYTIC PRODUCTION OF IRON FROM IRON SULFATE SOLU- TIONS Sigurd Arthur Aannerud and Eigil Mostad, Lokken Verk, Norway, assignors, by mesne assignments, to Pyror Limited, Pembroke, Bermuda, a. corporation of Bermuda No Drawing. Application May 12, 1950, Serial No. 161,746

Claims priority, application Norway May 27, 1949 2 Claims.

For the electrolysis of metal sulphate solutions it is usually not difficult to provide a diaphragm which aiiords a satisfactory current yield for the precipitation of the metal.

However, in the electrolytic production of iron from solutions of FeSOi specific problems arise, since diaphragm materials which are previously known for electrolytic processes and are sufiiciently resistant to the attack of chemicals in the electrolyte when used for this purpose, either have caused an undesirable high voltage drop and a consequent large power consumption per unit of electrolytic iron, or have not been capable to prevent, to the desired extent, a passage of electrolyte to the anode. The latter factor is important, because by the passage of electrolyte to the anode trivalent iron is formed, which entails undesired subsidiary reactions when the sulphuric acid from the electrolysis is returned in order to be used for forming new iron sulphate solution by leaching out iron from for example FeS.

By extensive experiments it has now been found that results which are entirely satisfactory in any respect can be achieved for the present purpose by using as a diaphragm a fabric of Vinyl chloride-acrylonitrile, which by a preceding heat treatment has been stabilized to a porosity convenient for the electrolysis. As it is known, this material is the condensation product of vinyl chloride and acrylonitrile, and in forming a fabric, the material is extruded through nozzles into fine filaments and is then spun and woven into fabric. The experiments show that apart from withstanding attack from the chemicals present, this material has absorbing properties suitable for the purpose, so that the voltage drop and hence the power consumption are kept within reasonable limits, and at the same time the shrinkage by the heat treatment permits an exact control of the pores of the tissue to a dimension suited for the iron electrolysis, so that undesired passage of electrolyte is avoided. More especially, with this material stabilized at about 150 centigrades with a shrinkage of about 12 to 16%, results have been obtained which are far superior to those which it has been possible to obtain with diaphragms previously used for electrolytic purposes.

We claim:

1. The process of recovering iron from aqueous solutions of iron sulphate which comprises the steps of (a) establishing an electrolytic cell containing a vinyl chloride-acrylonitrile resinous fabric diaphragm in which said iron sulphate solution is made the electrolyte, said resinous fabric diaphragm being stabilized at about C. and having a shrinkage of about 12 to 16 (b) subjecting said electrolyte to electrolysis across said diaphragm, and (c) recovering the iron released in said electrolytic cell.

2. The process of recovering iron from aqueous solutions of iron sulphate which comprises the steps of (a) treating ferrous sulphide with sulphuric acid, (b) establishing an electrolytic cell containing a vinyl chloride-acrylonitrile resinous fabric diaphragm in which said iron sulphate solution is made the electrolyte, said resinous fabric diaphragm being stabilized at about 150 C. and having a shrinkage of about 12 to 16%, (c) subjecting said electrolyte to electrolysis across said diaphragm, and (d) recovering the iron released in said electrolytic cell.

SIGURD ARTHUR AANNERUD. EIGlL MOS'IAD.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,007,388 Ramage Oct. 31, 1911 2,176,427 Kershaw Oct. 17, 1939 2,342,230 Weber et a1 Feb. 22, 1944 2,355,822 Rugeley Aug. 15, 1944 2,420,565 Rugeley May 13, 1947 FOREIGN PATENTS Number Country Date 196,334 Great Britain Apr. 23, 1923 OTHER REFERENCES U. S. Bureau of Mines Bulletin No. 463 (1946), Operation of Electrolytic Manganese Pilot Plant, page 72.

Ser. No. 288,035, Rudolph (A. P. C.), published May 18, 1943. 

1. THE PROCESS OF RECOVERING IRON FROM AQUEOUS SOLUTIONS OF IRON SULPHATE WHICH COMPRISES THE STEPS OF (A) ESTABLISHING AND ELECTROLYTIC CELL CONTAINING A VINYL CHLORIDE-ACRYLONITRILE RESINOUS FABRIC DIAPHRAGM IN WHICH SAID IRON SULPHATE SOULTION IS MADE THE ELECTROLYTRIC, SAID RESINOUS FABRIC DIAPHRAGM BEING STABILIZED AT ABOUT 150* C. AND HAVING A SHRINKAGE OF ABOUT 12 TO 16%, (B) SUBJECTING SAID ELECTOLYTE TO ELECTROLYSIS ACROSS SAID DIAPHRAGM AND (C) RECOVERING THE IRON RELEASED IN SAID ELECTROLYTIC CELL. 